Prior Art Statement
There are many well known techniques for breaking emulsions, for example, gravitational settling, centrifugation, heating, the application of electrical fields and the addition of salt or deemulsifiers to the emulsion. U.S. Pat. No. 3,245,466 teaches breaking oil-in-water emulsions obtained from the water flooding of an oil reservoir with a light hydrocarbon solvent for the crude oil in order to dissolve the crude oil from the emulsion, thereafter separating the mixture with gravity techniques. U.S. Pat. No. 3,491,835 utilizes gravity means to break heavy crude oil emulsions. However, these conventional means, in and of themselves, will not render a crude oil containing surfactant suitable for conventional refinery processes.
The use of alcohols in surfactant systems is also known. Alcohols have been used as cosolvents or cosurfactants to stabilize micellar dispersions containing water and oil. See, for example, U.S. Pat. Nos. 3,307,628, 3,520,365 and 3,682,247. Gale in U.S. Pat. No. 3,637,017 uses a dilute alcohol water drive solution as a stripping agent to increase the quantities of surfactant recovered from a formation, thereby increasing the quantity of oil recovered. Thereafter, the surfactant can be reused in the recovery operation. He also teaches the addition of alcohol to the surfactant flood which precedes the alcohol drive solution. Additionally, low molecular weight alcohols have been used in sulfonate manufacturing processes to extract oil raffinate from gas oil sulfonates. The alcohol is not removed from sulfonate and acts as a cosurfactant in the micellar dispersion which is formulated with the sulfonate. The prior art teaches the use of alcohol as an aid to a surfactant's solubilization of oil to form a more stable micellar dispersion of hydrocarbon, water and surfactant. It does not recognize the ability of small amounts of a low molecular weight alcohol to break the micellar formation allowing for the separation of water and surfactant from crude oil.
The use of surfactants in processes for the recovery of oil from subterranean formations may result in the produced oil containing 0.1% or more surfactant by weight. This surfactant can cause the oil to contain excessive water which is difficult to remove by conventional means and which makes it difficult to transport the produced oil. Such surfactants can also cause the formation of emulsions during conventional refinery desalting processes resulting from the addition of water to the produced oil. Thus, the process of the present invention provides not only for the removal of water, but also for the removal of surfactants from these micellar produced crude oils in order to prevent the formation of subsequent emulsions.